Various styles of rigs have been proposed for utilizing both coiled tubing and threaded tubulars to be selectively inserted through the rig floor and into the well. Rigs conventionally include a mast extending upward from a rig base when in an operative position. Rigs sometimes referred to as universal rigs include both a coiled tubing injector supported on the mast to insert coiled tubing into the well, and a top drive movable along an axis of the mast when in the operative position to insert a threaded tubular into the well.
Rigs with coiled tubing injectors have traditionally relied primarily upon the use of the coiled tubing to conduct downhole operations. Coiled tubing is thus conventionally used to suspend a downhole motor in the well, with fluid pumped through the coiled tubing to drive the downhole motor and drill the well. Other operations may also be conducted with coiled tubing in a manner more efficient than if conducted with threaded tubulars. Top drives have also been provided on the mast of universal rigs for inserting a threaded tubular into a well, although typically top drives have been used to threadably connect sections of a bottom hole assembly or to run surface casing in the well, and generally have not been used to drill substantial portions of the well. Accordingly, when a plurality of tubular joints are run in or out of the well utilizing the top drive, the tubular joints are threadably connected or disconnected, and are pulled up or laid down on the rig floor through the V-door of the rig. This operation takes a considerable amount of time and is thus costly.
One of the problems with rigs adapted for conducting both coiled tubing and conventional threaded tubular operations involves both the practical and government-imposed limitations on the weight for a trailer or other carrier being transported along public roadways to a rig site. Depending on the size of the drilling rig, the coiled tubing reel, the coiled tubing injector, the top drive, and the mast may all be supported on a single carrier. In other embodiments, the weight of these components does not allow for a sufficient amount of coiled tubing to be placed on the same carrier with the mast, the top drive, and the injector. Accordingly, an injector may be transported with the mast on a mast carrier separate from the coiled tubing reel on a coiled tubing carrier, in which case the end of the coiled tubing must be threaded through the injector before the injector becomes operational at the well site. Additional difficulties are encountered to safely release the coiled tubing from the injector after the coiled tubing operation is complete. In other applications, the mast is transported to the well site separate from the substructure which includes a work platform, and the mast is raised to extend upward from the work platform. Another carrier may be used to transport the coiled tubing reel to the well site. These difficulties have decreased the efficiency of coiled tubing units, and may be create safety problems.
The disadvantages of the prior art are overcome by the present invention, and an improved rig is hereinafter disclosed for selectively inserting coiled tubing or threaded tubulars into a well.